1. Field of the Invention
The present invention relates to air filters used in internal combustion engines, specifically a method of making a filter medium adapted for use in such air filters.
2. Description of the Related Art
Fluid streams such as air and gas often carry particulate matter. Because it is desirable to remove the particulate matter from the fluid stream, the air streams flowing to internal combustion (“IC”) engines generally need to be filtered before the particulate matter reaches the engine. In automobiles, air filters are used to filter the air streams and the air filters are commonly utilized upstream of the automobile's engine.
Air filters contain filter media that are often made of non-woven materials. A non-woven filter medium can be formed in a web by conventional non-woven techniques including melt-blowing, spunbonding, carding, air laying, wet laying, or the like. Melt-blown non-woven webs can be formed by the process generally taught in Wente, Van A., “Superfine Thermoplastic Fibers” in Industrial Engineering Chemistry, Volume 48, pages 1342-1346 (1956), or Report No. 4364 of the Naval Research Laboratories, published May 25, 1954, entitled “Manufacture of Superfine Organic Fibers” by Wente, Van A., Boone, C. D. and Feluharty, E. L. The melt-blowing process typically produces fine fibers with a diameter of less than ten (10) microns, and the use of the melt-blowing process allows the non-woven material to be formed in one step from a resin to a melt-blown non-woven material.
Melt-blown materials have found utility in a broad range of applications. For example, it is known to use melt-blown filaments in the preparation of battery separators, cable wrap, capacitor insulation paper, as wrapping materials, clothing liners, diaper liners, in the manufacture of bandages and sanitary napkins, and the like. Melt-blown materials have also been utilized as the filter media used in air filters.
Several processing steps are required to form non-woven filter media using the carding, air laying or wet laying techniques. For this reason, an improvement is needed in the art over these techniques to form filter media that may be adapted for use in air filters used in internal combustion engines. A technique is necessary that uses less equipment and preserves time, energy and money.